1. Field of the Invention
This invention relates to a paving machine and more particularly to a paving machine that covers the sloping surfaces of a diversion island for a power plant cooling pond with a continuous surface having a step-like configuration.
2. Description of the Prior Art
In cooling ponds for power plants the hot water discharged from the power plant is directed around a diversion island that separates the outlet of the power plant from the inlet. The diversion island directs the water a sufficient distance from the outlet to the inlet to permit the water to cool before it enters the inlet of the power plant. The diversion island is an earthen structure having surfaces that slope downwardly from a central peak that divides the inlet from the outlet. With this arrangement, the hot water is cooled as it circulates around the diversion island.
One problem that is encountered in the cooling of the water by this method is the generation of waves within the cooling pond under high wind conditions that divert the water over the diversion island. Subsequently, the hot water is directed from the outlet under the wave action over the diversion island into the portion of the cooling pond adjacent the inlet of the power plant. Consequently, the water does not circulate a sufficient distance to cool and, therefore, heated water is taken into the power plant. The wave problem is intensified by the smooth surfaces of the diversion island which present little or no resistance to the waves as they flow over the top of the diversion island. In addition, the wave action erodes the earthen diversion island and thereby diminishes the slope of the island.
To eliminate the interruption of the cooling process and the erosion problem generated by the wave action, the surface of the diversion island is paved in steps that extend longitudinally on the surface of the island. The steps serve to break up the wave action to thus prevent the hot water from flowing over the island and also to prevent erosion of the island. The known methods of constructing the step-like surface on the slopes of the diversion island require considerable effort and expenditure. First, forms for the step-like breakers must be constructed on the diversion island, and then castable material, such as concrete or an admixture of soil and cement, is poured into the forms. Upon curing, the step-like breakers are formed. Another alternative to erecting step-like breakers on the diversion island is precasting the breakers and then laying the precast breakers in strips upon the surface of the diversion island.
Paving devices in general are well known in the art, and particularly machines for paving canal linings as disclosed in U.S. Pat. No. 2,090,959, in which a method and apparatus is described for lining the inclined walls of canal with a uniform surface of concrete. An inclined frame is supported for movement parallel to the canal and includes a carriage that is movable on the frame above the surface to be paved. A screed is mounted on the carriage and is provided with a vibrator, which feeds the castable material such as concrete from a hopper. In this manner, a planar lining of concrete is applied to the inclined surface of the canal.
U.S. Pat. Nos. 2,707,422, 2,818,790, 3,427,938 and 3,710,695 disclose curbing machines that utilize a screw conveyor to transport concrete from a supply hopper to a distributing hopper. The distributing hopper then directs the concrete to its curved extruding shoe. U.S. Pat. No. 3,710,695 includes an elevating screw conveyor that is mounted on crawler tractors. The tractors include a linkage mechanism for compensating for deviations in the slope of the grade to be paved.
In addition, U.S. Pat. Nos. 3,225,668 and 3,107,592 describe machines for distributing concrete within forms that define a roadway to be paved. A pivotal conveyor transports concrete from a mixer into the roadway form. U.S. Pat. No. 3,693,512 illustrates and describes an elevating conveyor that lifts paving material from a hopper and conveys it to a discharge point. At the discharge point excess material is stored until it can be distributed by a paving machine.
There is need for a paving machine that continuously applies and casts material on the inclined surfaces of a power plant diversion island without the necessity of interrupting the process of applying the material onto the surface and of casting the material in a preselected configuration.